The application of coatings to large surface areas such as floors has various problems and difficulties. Various UV cure coatings have been developed, such as paints and varnishes, some being protective and some being decorative, or both. The molecules in these UV cure coatings become cross linked when exposed to UV radiation forming a hard curable surface. Water borne UV cure coatings have been developed which have water-like viscosity and are easy to apply. Their drawback, however, requires the water to evaporate before final curing. This may take several hours and is problematic in cold climates. The application of water borne UV coatings and the time required for curing produces several problems. Application and curing are done in two separate and time consuming steps, usually taking many hours. The final finish may be marred. Dust may settle and become trapped in the coating. Bubbles may be introduced during application and become trapped in the coating. Curing may be uneven due to irregular exposure to UV radiation, such as parts of a floor which may or may not be exposed to sunlight from a window. Also, thickness of the coating is difficult to control both. Thick coatings which provide protection are difficult to cure properly.
Recent advancements have produced UV curable polymers without solvents or other volatile compounds which evaporate from the liquid. They have yielded numerous high quality coatings which are first applied and then cured with portable UV lamps. Although these solventless UV curable coatings offer instant cure, they are used on small substrates such as small samples of wood, tile, stone, etc. Widespread use of these coatings has been limited on large surfaces such as floors due to problematic application processes which produce blemishes and a flawed appearance. Problems, which are deleterious to the coating's appearance, include dust, bubbles, particulates, and cure lines due to shrinkage and high viscosity. In addition, pigments and shrinkage also limit the thickness of the coatings. This is especially important where thicker coatings are needed to provide adequate protection, especially to surfaces such as floors.
Both chemical and physical solutions to application problems with solventless UV coatings are being attempted. Feathering the edge of reflectors, dithering the light source, modifying the coatings characteristics, and using novel rollers or brushes, are being tried with some success. Yet even with these solutions, coatings which are thick enough to provide adequate protection when applied in the field to surfaces such as floors, suffer from systematic problems associated with their surface tension, viscosity, and surface characteristics. Pigmented coatings are particularly troublesome and require special lamps for deep cure, and also require precise thickness control as do clear or satin like coatings. In addition, as with water borne UV coatings, this is a separate, time consuming, two-step process of application and then cure.
High quality very thin instant UV curable coatings are now successfully applied in the field with squeegee and cloth applicators on smooth wood, marble, stone, etc. However, the painstaking and time consuming manual application processes and lack of longevity and durability for such very thin coatings on floors are impractical.
A better way is needed to reduce the application and curing time, eliminate the introduction of blemishes into the cured coating, and easily and rapidly build a coating to a desired thickness.